1. Field of the Invention
This invention pertains to a microphone which picks up speech vibrations through the bone structure of an individual's skull and develops a signal for audio processing. More particularly, the present invention relates to an ear mounted microphone responsive to audio vibrations from the user's skull which are isolated from surrounding background environment and which can be used in duplex with a speaker positioned within a common housing with the microphone.
2. Prior Art
The emergence of computer based control systems for virtually every aspect of daily living has re-emphasized the need for an inexpensive system for providing direct voice command capability. At present, most computer systems rely on keyboard input to provide data and processing instructions. This is not only time consuming and limiting in view of physical requirements of being seated with both hands on a key pad, but it limits the efficiency of data input to the typing speed of the user. Indeed, compared with the advanced degree of sophistication of current computer systems, this dominant data entry method of imputing instructions one letter or number at a time seems almost archaic.
This is not to say that the development of voice activated input systems has been ignored. There has clearly been a long recognized need for implementation of a method of voice command which would obviate the keyboard as a computer input device. Numerous problems have remained unsolved, however, and continue to place voice activated systems beyond the financial reach of the general marketplace. For example, the typical level of confidence in voice recognition for commercial software is between 45 to 60%. At this rate, the system is averaging only one out of two words with correct identification. This is hardly adequate for general application. This confidence level is even less when environmental factors are introduced such as background noise, mobility of the user and other unpredictable variables that modify the audio signal being received at the computer.
In typical applications for voice activated systems, one might expect a telephone to ring during dictation, an interruption to occur by another voice having a different voice pattern, the sounding of a horn, clock alarm, or any of thousands of extraneous background noises. Even the shifting of position of the speaking individual can modify the audio signal enough to confuse the computer recognition of sounds. The speaker may simply turn her head to a different direction and create enough variation to thwart voice recognition.
Resolution of these anomalies must be accomplished before voice command systems can be of general use. Current efforts have focused on generation of complex algorithms which sift through the maze of audio signal and attempt to classify and discard background noise. Obviously, it is impossible to completely predict and program every potential superfluous signal that may eventually be detected. Voice variations by the user are even more challenging, because the occurrence of a cold, sinus problems, and variations in voice orientation to the microphone are extremely difficult to classify or quantify. As a consequence, voice command systems are marginal in overall performance and are extremely expensive.
Undoubtedly, part of the problem of voice recognition arises because of the use of conventional microphones as the media for processing voice signals. Voice recognition obviously requires conversion of the audio input to digital or analog signal. Generally, a digital conversion is necessary before comparison with database information is possible. A normal microphone will pick up sounds indiscriminately, thereby adding in background noise which is a primary source of confusion.
Although some discrimination of sound can be accomplished by frequency filters, proximity attenuators, and related devices that group sound characteristics as to common features of frequency or volume, total isolation of desired sounds has not generally been accomplished when the speaker is in a nonisolated environment. Development of such a selective microphone system has long been needed and would provide great advantage in countless applications. This is so with any form of telephone system that is hands free so that the microphone is picking up background signal along with the primary speaker's voice. Visor microphones for cellular car phones is just one of a myriad of examples. TV and stage cameramen, as well as other sound technicians who must communicate quietly while recording or producing video and sound works, require constant communication which functions best in an isolated mode. Switchboard operators, pilots, motorcyclists, workers having on line communication systems in high-noise environments--all need a communication system which isolates the voice signal from all extraneous sounds.
U.S. Pat. No. 4,588,867 by Konomi addressed some of these problems and disclosed the possible utility of an ear-mounted microphone for discarding air-borne sound waves in favor of bone conduction of the speaker's voice. Aside from technical problems which may have affected the inability of this device to perform adequately, practical considerations also limit the general acceptance of such ear-mounted microphone systems. For example, the Konomi device places a microphone element deep in the ear canal in order for vibrations to be accessed from the bone. This requirement immediately imposes the high cost of having the canal insert portion sized to the unique configuration of the user's ear canal as with a hearing aid. It also adds the discomfort of having an insert in the ear, creating an unnatural and unacceptable sensation which would undoubtedly preclude universal usage of the device.
As a further problem, the Konomi reference may be subject to audio feedback arising from the close proximity of the microphone element and speaker, where a duplex mode is selected. Needless to say, the challenge of an acceptable ear-mounted microphone was not resolved with Konomi.
U.S. Pat. No. 4,930,156 by Norris addressed the problem of audio feedback with its disclosure of an ear microphone/speaker combination; however, the microphone was placed outside the ear and was sensitive to ambient noise. The absence of isolation of the speaker voice gave the device only limited acceptance, despite the fact that it offered some improvement over the prior art.
What is needed therefore is a microphone that totally isolates the voice of the speaker from the environment, yet which is not limited by sizing for the ear canal or does not create discomfort by being fit within the ear canal.